maybe it's partly due to the change in attitude amongst modern recruits. "in the olden days" you turned up fit if you knew what was good for you, as they binned the cr*p ones - instead of today's emphasis on "training" them all. therefore they can turn up in shite state and still expect to get through. where is the motivation to prepare before arriving?
i sense there must have been a change in recruiting staff too. they used to be like the "bobby on the beat, clip round the ear" that is sadly missing nowadays. you were likely to be told "you go out and get f*cking fit before you report to depot, or else!"